1. Field of the Invention
An object of the present invention is an examination bed that can be adjusted in height, used for medical purposes and especially for tomography by scintigraphy. Its object is to enable a largeamplitude vertical shifting Of the bed. It enables the bed to be located, in the maximum position, at a height from the ground that is twice as great as its low position.
2. Description of the Prior Art
At present, for tomography by scintigraphy of organs of the human body, a patient to be examined is made to recline on an examination bed, the organ to be examined being placed before a detector of a gamma camera. The tomography examination consists in acquiring one image, in projection, of the organ per angle of view, for a large number of angles of view. These angles of view are evenly spaced out over an angular sector of at least 180.degree.. They are obtained by making the detector of the gamma camera pivot about the patient. It is then possible to use computation algorithms to reconstitute the image of the volume examined from the images in projection.
In an as yet unpublished French patent application No. 91 06962, filed on 7th Jun. 1991, a gamma camera with two detector heads is used for the tomography of organs of the human body, the point aimed at by the detector heads being offset with respect to the rotational axis of the gamma camera. To this end, the detector heads are made to perform angular motions that are symmetrical in relation to the horizontal plane. This implies that the fields of detection of the two detector heads are no longer parallel. Then, the gamma camera and, consequently, the detector heads are made to pivot, one and the same location in the human body being kept as the point aimed at during the rotation.
However, since the point aimed at is offset in relation to the rotational axis of the gamma camera, the gamma camera must be moved in a lateral translational motion while the bed is moved in an ascending motion.
Nevertheless, a major problem arises for it is necessary, in this case, to provide for a bed whose low position is located at 55 centimeters above the ground while its high position is at about 120 centimeters, the shifting of this bed being done vertically. Now, at present, the beds generally used in hospitals are beds whose underframe is X-shaped. These beds have a first drawback which is that they rise not vertically but in describing a circular arc. A second drawback arises out of the fact that the X-shaped underframe leaves a clearance under the bed that is not always the same depending on whether the bed is in the high position or in the low position. Apart from this approach, there is no possibility of having examination beds whose range of elevation has a factor of two or even more. Furthermore, given the weights involved (in the range of a ton given the safety coefficients), any structure that can be envisaged is either too heavy or too flimsy.